Selective viewing of a scene

ABSTRACT

Among other disclosed subject matter, a computer-implemented method for performing selective viewing of a scene includes acquiring an image of a real scene using a camera. The method includes identifying, in the acquired image, a first object in the real scene located on a first side of a virtual plane defined for the real scene and a second object located on a second side of the virtual plane. The method includes modifying the acquired image by removing image content corresponding to the identified first object, wherein image content corresponding to the identified second object is not removed based on the second object being located on the second side. The method includes displaying the modified acquired image for a person to view the real scene.

This application is a divisional application (and claims the benefit ofpriority under 35 U.S.C. §121) of U.S. application Ser. No. 12/136,242,filed Jun. 10, 2008. The disclosure of the prior application isconsidered part of (and is incorporated by reference in) the disclosureof this application.

TECHNICAL FIELD

This document relates to selective viewing of a scene.

BACKGROUND

Camera surveillance is frequently used, particularly since the advent ofmotion cameras that register live images of a scene. For example,surveillance cameras are often used to monitor entrances, importantobjects and other items of interest. Many types of cameras andphotographic techniques have been developed, including conventionalvideo cameras that record moving images on a magnetic tape, for example.Digital image recording is sometimes used.

A situation that can occur is that there is something sensitive orsecret in the view of the surveillance camera. There are sometimes lawsand/or other regulations as to what matter a surveillance camera cancapture. For example, such laws may deem it acceptable to direct thecamera toward a private doorway but not to capture any view of a publicsidewalk just beyond the doorway. As another example, camerasurveillance may be performed to guard matters of great importance, suchas classified military premises or trade secret laboratories, againstunauthorized people. However, the surveillance operation can be mademore difficult if the important object or premise is not to be shown tothe person tasked with watching the surveillance image (i.e., thesecurity guard). Attempts at performing surveillance have includedmasking of a portion of the camera image. However, this mayunintentionally obstruct also important parts of the image, and it canrender the camera image unnatural and difficult to survey.

SUMMARY

The invention relates to selective viewing.

In a first aspect, a computer-implemented method for performingselective viewing of a scene includes acquiring an image of a real sceneusing a camera. The method includes identifying, in the acquired image,a first object in the real scene located on a first side of a virtualplane defined for the real scene and a second object located on a secondside of the virtual plane. The method includes modifying the acquiredimage by removing image content corresponding to the identified firstobject, wherein image content corresponding to the identified secondobject is not removed based on the second object being located on thesecond side. The method includes displaying the modified acquired imageto a person performing surveillance of the real scene.

Implementations can include any, all or none of the following features.The image can be acquired as part of continuously acquiring a live imageof the real scene, and during a duration of the acquired live image thefirst object can move between a location behind the virtual plane and alocation in front of the virtual plane, as seen from the camera. Themethod can further include modifying the acquired live image so that thefirst object is visible in the modified acquired live image only whenthe first object is in front of the virtual plane. The method canfurther include modifying the acquired live image so that the firstobject is visible in the modified acquired live image only when thefirst object is behind the virtual plane. A shape can define the virtualplane, and the method can further include replacing any image contentswithin the shape with substitute content that does not include the firstobject. The method can further include acquiring the substitute contentby acquiring another image of the real scene while the first object isnot present on the first side of the virtual plane. A shape can definethe virtual plane, and the method can further include determining thatthe first object is on the first side by identifying that image contentcorresponding to at least part of the first object has a predefinedlocation relative to a border of the shape. The image can be acquired aspart of continuously acquiring a live image of the real scene, and themethod can further include modifying the acquired live image by erasingany image content within the shape and placing substitute content withinthe shape that does not include the first object; identifying that thefirst object moves in the real scene, wherein the first object is notvisible in the modified acquired live image while the first object is onthe first side; determining, based on the identification, that the firstobject moves past the shape to the second side; and ceasing to removecontent corresponding to the first object from the modified acquiredlive image based on the determination. The method can further includedetermining that the first object is on the first side by analyzing asize of the first object in the acquired image using a map of the realscene. The method can further include determining that the first objectis on the first side by determining a distance from the first object tothe camera. The first object can be a human being and the distance canbe determined using a size of a part of the human being measured in theacquired image. The virtual plane can be defined at a specific locationin a passageway in the real scene such that any object passing throughthe virtual plane in the passageway is only visible in the modifiedacquired image while on one of the first and second sides. The virtualplane can be defined by a virtual polygon. The modified acquired imagecan be displayed to the person substantially in real time. The modifiedacquired image can be displayed for low-security level observation, andthe method can further include recording the acquired image forhigh-security level observation. A shape can define the virtual plane,and the shape can include at least one hole.

In a second aspect, a computer program product is tangibly embodied in acomputer-readable storage medium and includes instructions that whenexecuted by a processor perform a method for performing selectiveviewing of a scene. The method includes acquiring an image of a realscene using a camera. The method includes identifying, in the acquiredimage, a first object in the real scene located on a first side of avirtual plane defined for the real scene and a second object located ona second side of the virtual plane. The method includes modifying theacquired image by removing image content corresponding to the identifiedfirst object, wherein image content corresponding to the identifiedsecond object is not removed based on the second object being located onthe second side. The method includes displaying the modified acquiredimage for a person to view the real scene.

In a third aspect, a computer-implemented method for performingselective viewing of a scene includes continuously acquiring a liveimage of a real scene using a camera, a virtual polygon being definedfor the real scene. The method includes identifying, in the acquiredlive image, an object that is moving in the real scene. The methodincludes determining that during a duration of the acquired live imagethe object moves from a first side past the virtual polygon to a secondside, the determination performed by identifying that image contentcorresponding to at least part of the object crosses a border of thevirtual polygon, as seen from the camera, as the object moves past thevirtual polygon. The method includes modifying the acquired live imagebased on the determination so that the object is visible in the modifiedacquired live image only while located at one of the first and secondsides. The method includes displaying the modified acquired live imagesubstantially in real time for a person to view the real scene.

Implementations can include any, all or none of the following features.The first side can be behind the virtual polygon, and the second sidecan be in front of the virtual polygon, as seen from the camera, and themodification can be performed so that the object is visible in themodified acquired live image only while the object is in front of thevirtual polygon as seen from the camera. The first side can be behindthe virtual polygon, and the second side can be in front of the virtualpolygon, as seen from the camera, and the modification can be performedso that the object is visible in the modified acquired live image onlywhile the object is behind the virtual polygon as seen from the camera.

In a fourth aspect, a computer-implemented method for performingselective viewing of a scene includes acquiring an image of a real sceneusing a camera, wherein a virtual shape has been defined for the realscene. The method includes modifying the acquired image by removingcontent forming at least a portion of the virtual shape, the removedcontent being located on a first side of the virtual shape in the realscene, wherein non-removed content of the virtual shape being located ona second side of the virtual shape in the real scene. The methodincludes displaying the modified acquired image substantially in realtime for a person to view the real scene.

In a fifth aspect, a computer-implemented method for performingselective viewing of a scene includes acquiring an image of a real sceneusing a camera. The method includes identifying at least a first featurein the acquired image based on the first feature moving in the realscene, wherein the real scene further includes a second feature that isnot moving in the real scene. The method includes modifying the acquiredimage by removing the first feature and not removing the second feature.The method includes displaying the modified acquired image for a personto view the real scene without the first feature.

Implementations can provide any, all or none of the followingadvantages. Scene viewing can be improved. Camera surveillance can beimproved. A real scene that includes sensitive or unwanted matter can beselectively viewed so as to exclude the matter from an image watched bysecurity personnel. Image objects can selectively appear or disappear incamera images based on the object changing its distance relative to thecamera. A camera image can be provided that looks natural and is easy tosurvey. Image-enhancing properties can be provided, for example higherresolution and/or less noise.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features and advantages willbe apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIGS. 1A-2C show example acquired images and modified imagescorresponding to a real scene captured by a surveillance camera.

FIG. 3 is a block diagram showing an example relationship between asurveillance camera, a virtual polygon, and objects in a real scene.

FIG. 4 is a flow chart showing an example process for performingselective surveillance of a scene.

FIG. 5 is a flow chart showing an example process for continuouslyacquiring an image of a real scene.

FIG. 6 is a block diagram of a computing system that can be used inconnection with computer-implemented methods described in this document.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

FIGS. 1A-1C and 2A-2C show example acquired images 102 a-102 f andmodified images 104 a-104 f corresponding to a real scene captured by asurveillance camera. For convenience, the FIGS. will be described inreference to a surveillance system. In general, the surveillance systemis configured to perform selective surveillance. For example, thesurveillance system can omit one or more regions of a real scene as toosensitive to be viewed by security personnel. As another example, thesurveillance system can omit a region of a real scene that does notcorrespond to property owned by an organization utilizing thesurveillance system.

The acquired images 102 a-102 f correspond to a real scene that iscaptured by the surveillance camera. For example, the real sceneinvolves a corridor of an organization, wherein security surveillance isbeing performed. Over time, the acquired images 102 a-102 f arecontinuously updated to reflect the current state of the real scene(e.g., in some implementations the acquired images 102 a-102 f can beselected snapshots from a live image). For example, when the acquiredimages 102 a-102 f are updated they can reflect a change in thepositioning of a person 106 who moves through the corridor.

A corresponding modified image 104 a-104 f, respectively, can begenerated according to how the surveillance system is configured. Forexample, the modified images 104 a-104 f correspond to their respectiveacquired image 102 a-102 f optionally with a portion of the contentremoved. In some implementations, this provides that a person performingsurveillance can be shown any or all of the modified images 104 a-104 f,or the live image stream corresponding to the modified images 104 a-104f, and not any of the acquired images 102 a-102 f. Such an approach canallow the person to perform the necessary surveillance without seeingsensitive image information, i.e., the removed contents. In someimplementations, the acquired images 102 a-102 f are not shown to theperson performing the surveillance. That is, only the modified images104 a-104 f are then presented to the person performing thesurveillance. In some implementations, if the acquired images 102 a-102f are not generally presented, the system may nevertheless allow theacquired images 102 a-102 f to be presented, in real time and/or at alater time, upon receipt of a password or some other form of securitycredentials (e.g., biometric information or RFID tag), to name twoexamples. For example, the acquired images 102 a-102 f, modified images104 a-104 f, or both may be encrypted using any number of conventionalencryption techniques. Additionally, upon receipt of a password or othersecurity credentials, any of the images 102 a-102 f and 104 a-104 f canbe decrypted and presented in real time or during a later review of acaptured surveillance video.

Moreover, in some implementations, either acquired images 102 a-102 f,modified images 104 a-104 f, or both can be recorded. For example,consider a situation where a security alarm is triggered. Upon receiptof an alarm signal, the surveillance system can capture a recording ofthe event(s) that is provided to security personnel. That is, themodified images 104 a-104 f can be recorded on computer readable media(e.g., a hard drive, flash drive, optical disk, tape, or any otherconventional storage media) and provided to security personnel at somelater time. In some implementations, instead of recording both acquiredimages 102 a-102 f and modified images 104 a-104 f, modified images 104a-104 f are recorded with additional information that describes atransformation from the modified images 104 a-104 f to the acquiredimages 102 a-102 f. That is, the modified images 104 a-104 f can berecorded along with one or more transformations (e.g., image deltas)that allow the system to recreate the acquired images 102 a-102 f fromthe modified images 104 a-104 f using the transformation information. Insome implementations, these transformations may be applied only uponreceipt of a password or other security credentials.

That is, in a particular example, an employee without security clearancecan be allowed to view the modified images 104 a-104 f. Because thisobservation does not require a security clearance and/or the images arenot encrypted, for example, it can be considered a low-security levelobservation. Another person, in contrast, who has the required securityclearance, can be permitted to view the acquired images 102 a-102 f. Insome implementations, the acquired images 102 a-102 f are recorded in anencrypted form. Because this observation requires security clearanceand/or the image is encrypted, for example, it can be considered ahigh-security level observation.

Objects that move between successive acquired images can be identifiedby the surveillance system. For example, as the person 106 moves throughthe corridor, their position changes in the acquired images 102 a-102 f.Using the change in position between images, the surveillance system canidentify that the person 106 is moving. The objects that move can befurther analyzed to determine if they should be included in the modifiedimage, or excluded from the modified image. For example, thesurveillance system determines if the person 106 should appear in any ofthe modified images 104 a-104 f according to the person's position inthe real scene. Example determinations include, but are not limited to,a determination according to an object's size, distance from the camera,other metrics generated by analyzing the acquired images 102 a-102 f, orcombinations thereof.

In general, a virtual plane can be defined that specifies a region inthe modified image. Objects on a particular side of the virtual planemay be included in the modified image and objects on the other side ofthe virtual plane may be excluded from the modified image. As oneexample, in reference to FIGS. 1A-2C, objects on the near side of (i.e.,in front) a virtual polygon 108 are displayed while objects on the farside of (i.e., behind) the virtual polygon 108 are excluded from themodified images 104 a-104 f.

Here, the virtual polygon is formed by a two-dimensional shape definedin a computer system that receives and processes the acquired images 102a-f. The virtual polygon 108 defines a virtual plane in the real scene.The virtual plane can extend in any direction and be placed anywhererelative to the real scene. In addition, more than one virtual plane canbe specified for any particular real scene. For example, an additionalvirtual plane may be optionally specified to remove objects located inan office 110. In other words, an additional virtual plane can be placedin front of the office's window and configured such that objects behindthe virtual plane are excluded from the modified images. That is, theremay be many virtual walls configured to remove objects in any number ofregions in the acquired images 102 a-102 f. Furthermore, the virtualplane can be shaped in any form including free-form shapes or any otheramorphous shapes, to name two examples. In some implementations, thevirtual wall may include at least one hole. An example of a holes isdescribed in more detail below.

The virtual plane can be defined in many different ways, such as using avirtual polygon or any other shape. For example, in reference to FIGS.1A-2C, the virtual polygon 108 is used to define the virtual plane. InFIGS. 1A-2C, the virtual polygon 108 is shown visible for clarity ofdescription, but in some implementations, the virtual polygon or othershape may not be visible to someone viewing the modified images 104a-104 f. As one example, a surveillance system application can beconfigured to display or remove the virtual polygon 108 according toreceived user input.

Moreover, the virtual plane can be configured so that the systemdisplays objects that are in front of the virtual plane and removesobjects that are behind the virtual plane. As another example, thevirtual plane can also be configured so that the system displays objectsthat are behind the virtual plane and removes objects that are in frontof the virtual plane. In general, when objects are removed to form amodified image, a portion of the acquired image that contained theremoved objects can also be removed. For example, a portion of theacquired image corresponding to the virtual polygon 108 in modifiedimages 104 a-104 f can be removed. In FIGS. 1A-2C, the modified images104 a-f are shown such that certain content (with the appearance of theremainder of the corridor) is seen inside the virtual polygon 108.However, as will be described below, such content within the virtualpolygon need not be an actual image from the scene, or may not have beencaptured at the same time as the rest of the content in the modifiedimage; rather, dummy contents can be placed inside the virtual polygonto give the otherwise live image of the real scene a natural appearance.

That is, in some implementations, a portion of the modified image thatis excluded can be replaced with substitute content. For example, inreference to FIGS. 1A-2C, the region of the image specified by thevirtual polygon 108 can be sampled over time in the acquired images 102a-102 f to generate a substitute image used to replace the regiondefined by the virtual polygon 108 when generating a modified image(e.g., any of modified images 104 a-104 f). In other words, a substituteimage can be generated for the region corresponding to the virtualpolygon 108 by averaging appropriate pixel values in the acquired images102 a-102 f over time. In some implementations, the substitute image canbe generated by averaging each of the previously captured acquiredimages. For example, in reference to FIGS. 1A-2C, the substitute imagefor modified image 104 f can be generated by averaging the appropriatepixel values of all of the acquired images 102 a-102 f. In otherimplementations, the substitute image can be generated by averagingappropriate pixel values in a subset of the acquired images 102 a-102 f.

The surveillance system can determine the position of an object in thereal scene according to a location of a portion of the object. Forexample, if the base of the object is lower on the image than the lowestportion of the virtual plane, then the object can be considered to be infront of the virtual plane. Moreover, the system can determine ifportions of objects (e.g., the feet, head, and/or arms of person 106)can be considered to be part of a single object. For example, a gradientthat specifies the movement of each portion of each object can bedetermined. Portions of objects with substantially similar gradients maybe considered to be the same object. In addition, a distance measurementcan be used to calculate the position of the object in the image. Forexample, a transformation can be constructed using the perspective viewof the surveillance camera and a map of the area that is being acquired.The transformation can be applied to the objects in the images todetermine a distance between the objects and the surveillance camera.

In reference to FIGS. 1A-1C, the person is walking away from thesurveillance camera. The images shown in reference to FIGS. 1A-1C aresnapshots of a time sequence of live images (i.e., in a video clip). Forexample, the acquired images 102 a-102 c show the person 106 walkingaway from the surveillance camera along a corridor. The modified images104 a-104 b, in contrast, show the person 106 as they are walking onlyuntil the person 106 reaches a predetermined distance from the viewer inthe corridor and thereafter the person will not be visible in themodified image 104 c or any other modified image in which the person 106is beyond the predetermined distance.

As noted above, FIGS. 1A-1C show a real scene where a person walks awayfrom a surveillance camera along a corridor. Particularly, FIG. 1Arepresents the real scene where the person 106 first appears in the viewof the surveillance camera. As illustrated in the examples of FIG.1A-1C, the virtual polygon 108 in the modified image 104 a is filledwith substitute content. That is, some or all the image contents insidethe virtual polygon 108 in these figures is not the actual imagecontents from the acquired images but rather some other contents. Forexample, because the person 106 is determined to be on the second sideof the virtual plane (e.g., the base of the person (e.g., the person'slegs) is below the base of the base of the virtual plane), the systemdoes not exclude the person from the modified image 104 a. This can meanthat only the part of the virtual polygon outside the person's upperbody is replaced with substitute content.

FIG. 1B represents the real scene where the person is on the verge ofcrossing a threshold between the first side of the virtual plane and thesecond side of the virtual plane. Because the base of the person (e.g.,the person's feet) is still slightly below the base of the virtualplane, the system does not exclude the person from the modified image104 b. In addition, because the position of the person is determined tobe at the threshold of the virtual plane 108, the person's positiontriggers the removal process that is illustrated in FIG. 1C.

FIG. 1C represents the real scene where the person continues to walkaway from the virtual camera. Because the person is determined to be onthe first side of the virtual plane (e.g., the base of the person isabove the lower border of the virtual plane), the system excludes theperson from the corresponding modified image 104 c. In contrast, theperson remains visible in the acquired image 102 c. In addition, becausethe person 106 is excluded from the modified image, the substitute imagegenerated for the virtual polygon 108 substantially fills the virtualpolygon 108. Because the modified image in this example has substitutecontent that looks like the far end of the corridor, the image looksnatural and is easy to survey. In some instances, the modified image 104c is essentially indistinguishable from an acquired (unmodified) imageof an empty corridor where no content has been excluded and that doesnot have any substitute content.

In reference to FIGS. 2A-2C, the person is now instead walking towardthe surveillance camera. As described in reference to FIGS. 1A-1C, theimages shown in reference to FIGS. 2A-2C are snapshots of a timesequence of live images (i.e., in a video clip). For example, theacquired images 102 d-102 f show the person 106 walking toward theviewer along a corridor. The modified images (e.g., modified image 104f) show the person 106 only after the person 106 reaches a predetermineddistance from the viewer in the corridor. Prior to reaching thepredetermined distance, the person 106 is not visible in the modifiedimages (e.g., in modified images 104 d-104 e) although the person isincluded in the acquired images 102 d-f.

FIG. 2A represents the real scene where the person 106 begins to walktoward the surveillance camera from the far end of the corridor. Becausethe person 106 is determined to be on the first side of the virtualplane, the system continuously excludes the person 106 from thecorresponding modified image 104 d. In addition, because the person 106is excluded from the modified image, the substitute image generated forthe virtual polygon 108 substantially fills the virtual polygon 108.

FIG. 2B represents the real scene where the person 106 has just crossedthe threshold between the first side of the virtual plane and the secondside of the virtual plane. Because the system has detected that theperson's feet are below a border of the virtual polygon, and thus theperson is on the second side of the virtual plane, the system triggersthe cessation of the exclusion of the person 106 from the modifiedimages that is illustrated in FIG. 2C.

FIG. 2C represents the real scene where the person continues to walktowards the surveillance camera. Because the person is determined to beon the second side of the virtual plane, the system does not exclude theperson from the modified image 104 f. The person is therefore visible inthe modified image 104 f. In addition, because the person 106 is notexcluded from the modified image, only the part of the virtual polygon208 outside the person's body is replaced with substitute content.

In some implementations, the distance between an object and thesurveillance camera can be determined based on a size of the object. Forexample, when the object is a human being, their distance can bedetermined based on registering the face of the person and measuring thesize of the face. Because human faces (e.g., of adults) tend to beapproximately of similar size, the measured size can be used to estimatehow far away the person is from the surveillance camera. Other distancedetermination techniques can be used.

Some examples herein describe the use of a surveillance cameras. In someimplementations, however, the techniques described herein may be used inother image capture activities that do not involve a surveillancecamera. For example, consider a situation where a photographer wants tocapture an image of a road where cars are constantly driving by so thephotographer cannot get a clear shot. By specifying one or more virtualwalls, the photographer can selectively remove the cars from the scene.As another example, consider a situation where a tourist wants to take apicture of their wife in front of the Sphinx but lots of other peopleare moving around in the background. By specifying one or more virtualwalls, the tourist can remove the other people, generating an image ofjust his wife and the Sphinx. That is, a camera (e.g., still camera,mobile phone camera, web-camera, or other cameras) may be configuredwith an application that allows any photographer to selectively removeone or more objects from a photograph by specifying one or more virtualwalls.

Another exemplary implementation is to selectively remove certainsubject matter from a scene. For example, assume that a person seeks tomake a video recording of someone standing in or near a busy location(e.g., Times Square). An unmodified video recording of the person islikely to have some amount of traffic visible in the view. With properimage processing, however, some of all of the traffic content can beselectively removed to form a modified video recording that containsless or no traffic in the view but which retains the stationary elementsof the real scene, such as surrounding buildings, which may be ofgreater interest. In some implementations, therefore, such processingcan be performed by defining a virtual plane that covers the whole imagesought to be captured (i.e., not merely covering a portion of the imageas described in another example herein). Based on the defined virtualplane, objects or other features that move in the real scene (e.g., thetraffic) can be identified based on their motion. These identifiedfeatures can then be selectively removed when generating a modifiedvideo recording. Buildings, people standing still, and/or othernon-moving or slow-moving features, in contrast, can be left in themodified image.

For example, an image of a real scene such as a landscape can beacquired using a camera. This can be a relatively sophisticated camerasuch as those often used in shooting full-length motion pictures, or aconsumer market camera such as those often used by individuals onvacation, to name a few possibilities. A first feature can be identifiedin the acquired image based on the first feature moving in the realscene. For example, one or more cars, taxis or buses can be identifiedbased on their motion. The real scene can further include a secondfeature that is not moving in the real scene. For example, this caninclude a person standing relatively still and/or a building. Theacquired image can be modified, either by processing performed in thecamera or by separately processing recorded information, to remove thefirst feature but not the second feature. The modified acquired imagecan be displayed for a person to view the real scene without the firstfeature. For example, the modified image can be displayed as a playbackfunction on the consumer camera or as part of the created motionpicture.

Processing of an acquired image can have further advantages. Forexample, an algorithm used in removing image features according to someexamples described herein can have image-enhancing properties. In someimplementations, an acquired landscape picture that is modified canappear to have higher resolution with less noise than the cameraproduces when taking a single snapshot (i.e., an ordinary photo).

FIG. 3 is a block diagram schematically showing an example relationshipbetween a surveillance camera 302, a virtual polygon 304, and objects306 and 308 in the real scene. The surveillance camera 302 can be anycamera. Examples include various dome cameras, color cameras,progressive scan cameras, mobile phone cameras, web-cams, or anotherwireless or wireline camera available from multiple vendors. Thesurveillance camera 302 is capable of acquiring a number of imagescorresponding to a live feed of a real scene, or snapshots thereof, toname a few examples. In general, the number of images captured during aparticular time interval corresponds to how the surveillance camera isconfigured. For example, one surveillance camera may be configured tocapture 10 frames (i.e., images) per second, while another surveillancecamera may be configured to capture 30 frames per second.

A virtual polygon (e.g., polygon 304) can be defined in a computersystem to which the surveillance camera is connected to provide thatobjects on a particular side of the virtual polygon are included in themodified images and objects on the other side of the polygon areexcluded from the modified images. For example, the virtual polygon 304can be used to define a virtual plane. If the virtual polygon has asufficient size compared to the physical configuration of the realscene, objects cannot circumvent the inclusion and/or exclusion bymoving through areas not covered by the virtual polygon 304. In thefollowing description of the example shown in FIG. 3, the terms “virtualplane” and “virtual polygon” are sometimes used interchangeably.

Over time, objects may move within the real scene. For example, eitherof objects 306 and 308 may move. In some scenarios, the objects 306 and308 may cross over to a different side of the virtual polygon 304. Forexample, object 306 may cross from the front of the virtual polygon 304to the back of the virtual polygon 304. In some implementations, when anobject crosses the threshold of the virtual polygon 304, thesurveillance system triggers the execution of one or more processes ofinclusion and/or exclusion. Moreover, objects may cross to differentsides of the virtual polygon 304 any number of times and are excluded orincluded in the modified images accordingly.

In some implementations, objects that are determined to be in front ofthe virtual polygon 304 are removed while objects behind the virtualpolygon 304 remain. For example, the system can determine the locationof the base of object 306 and/or object 308. Because the base of object306 is determined to be below the base of the virtual polygon 304,object 306 can be removed when generating a modified image. Conversely,if the base of object 308 is determined to be above the base of thevirtual polygon 304, object 308 can be included when generating amodified image. In other implementations, objects that are determined tobe behind the virtual polygon 304 can be removed while objects in frontof the virtual polygon 304 can remain.

In some implementations, the virtual plane 304 is a free-form shape andmay include one or more holes 310. For convenience, the hole 310 isdepicted as a circle, however, the hole may be of any shape or size andmay occupy any position within the virtual plane 304. The hole 310 canbe generated when the virtual wall 304 is specified, or can be generatedafter the virtual plane 304 is specified. For example, the securitypersonnel may provide user input corresponding to one or more drawingoperations on the virtual plane 304. In response, the surveillancesystem generates a hole 310 of a particular shape and size according tothe received user input. In contrast to the virtual wall 304, the hole310 does not remove objects from the modified image. For example, if thevirtual plane 304 is configured to remove objects that are in front ofthe virtual plane 304, the hole 310 may present any or all of object306, if portions of object 306 are inside hole 310 as seen from thecamera 302. As another example, if the virtual plane 304 is configuredto remove objects that are behind the virtual plane 304, the hole 310may present any or all of object 308, if portions of object 308 areinside hole 310 as seen from the camera 302. That is, the virtual plane304 can include one or more regions where objects are not removed,allowing the security personnel to see portions of objects in the hole.

FIG. 4 is a flow chart showing an example process 400 for performingselective viewing of a real scene. Process 400 can be performed by aprocessor executing instructions in a computer-readable medium. In someimplementations, the process 400 can be executed continuously accordingto the configuration of a surveillance system. For example, if thecamera is configured to capture 30 images per second, process 400 may beexecuted with a suitable frequency to process images captured at thatpace.

In step 410, the system acquires an image of a real scene using acamera. For example, in reference to FIGS. 1A and 3, camera 302 can beused to acquire image 102 a. The acquisition of the image can beaccomplished using any of a number of techniques and/or camera types.

Once the system acquires the image, in step 420, the system identifies afirst object in the real scene located on a first side of a virtualplane and a second object located on a second side of the virtual plane.For example, in reference to FIG. 1A, the far end of the corridor can beidentified as being on the first side, and the person 106 on the secondside, of the virtual polygon 108. Similarly, in FIG. 2A, the office 110can be identified as being on the first side, and the person 106 on thesecond side, of the virtual polygon 108.

In step 430, the system modifies the acquired image by removing imagecontent corresponding to the identified first object. Moreover, imagecontent corresponding to the identified second object is not removedbased on the second object being located on the second side. Forexample, in reference to FIG. 1A, the person 106 is not removed but thefar end of the corridor is replaced in the modified image withsubstitute content. Similarly, in FIG. 2A, the office 110 is not removedbut the person 106 is replaced in the modified image with substitutecontent. Examples of modifying acquired images are described below.

In step 440, the system displays the modified image for a person to viewthe real scene. For example, in reference to FIGS. 1A-2C, modifiedimages 104 a-104 f can be displayed to a security guard on any kind ofdisplay device. In these implementations, the modified images 104 a-104f may be displayed without displaying the acquired images 102 a-102 f.In addition, in some implementations, the modified images 104 a-104 fmay be displayed without displaying the virtual polygon 108.

FIG. 5 is a flow chart showing an example process 500 for continuouslyacquiring a live image of the real scene. Process 500 can be performedby a processor executing instructions in a computer-readable medium. Insome implementations, process 500 can be executed during process 400.For example, process 500 may be executed during step 430 of process 400.

In step 510, the system modifies the acquired live image by erasing anyimage content within the virtual polygon and placing substitute contentwithin the polygon that does not include the first object. For example,in reference to FIG. 1A, the system can erase the content correspondingto the far end of the corridor inside the virtual polygon 108.

In step 520, the system identifies that the first object moves in thereal scene. The system can use any applicable motion detection algorithmto detect the motion of the objects in the scene. One example motiondetection algorithm is core background subtraction. In general, corebackground subtraction ignores or otherwise disregards a portion of theimage that is determined to be substantially similar to a previousimage. In some implementations, the pixel values can be compared todetermine if they contain substantially similar values. For example, inreference to FIGS. 1A and 1B, if core background subtracting were usedon the acquired image 102 b, the system may ignore everything but theperson 106 and the nearby area around person 106, because only thosepixel values would be substantially different between the images 102 aand 102 b.

In step 530, the system determines based on the identification in step520 that the first object moves past the virtual polygon to the secondside. In general, the system determines the location of the base of theobject and compares it to the base of the virtual polygon. For example,in reference to FIG. 2B, the system determines that the base of person106 has moved past the virtual polygon 108 (e.g., as illustrated by theperson's feet in the modified image 104 e).

In step 540, the system ceases to remove content corresponding to thefirst object from the modified acquired live image based on thedetermination in step 530. For example, in reference to FIG. 2C, thesystem ceases to remove person 106 when generating the modified image104 f. That is, the person 106 is included in the modified image 104 f,and the virtual polygon 108 is partially filled with content in areas ofthe virtual polygon 108 that do not include the person 106.

In some implementations, the camera can pan. In such implementations,step 520 may be modified to account for the motion of the camera whendetermining which objects are moving in the scene. For example, opticalflow may be used to track objects through a series of acquired images ofthe real scene. That is, the motion of the camera can be measured andsubtracted from the motions of the objects determined by the system.This approach allows the system to determine which objects are movingrelative to each other, and which objects are only moving relative tothe camera. In such implementations, the objects that move relative toeach other are identified and a determination is made by the system ifthose objects should be included or excluded from the modified images asdescribed above.

FIG. 6 is a schematic diagram of a generic computer system 600. Thesystem 600 can be used for the operations described in association withany of the computer-implement methods described previously, according toone implementation. The system 600 includes a processor 610, a memory620, a storage device 630, and an input/output device 640. Each of thecomponents 610, 620, 630, and 640 are interconnected using a system bus650. The processor 610 is capable of processing instructions forexecution within the system 600. In one implementation, the processor610 is a single-threaded processor. In another implementation, theprocessor 610 is a multi-threaded processor. The processor 610 iscapable of processing instructions stored in the memory 620 or on thestorage device 630 to display graphical information for a user interfaceon the input/output device 640.

The memory 620 stores information within the system 600. In oneimplementation, the memory 620 is a computer-readable medium. In oneimplementation, the memory 620 is a volatile memory unit. In anotherimplementation, the memory 620 is a non-volatile memory unit.

The storage device 630 is capable of providing mass storage for thesystem 600. In one implementation, the storage device 630 is acomputer-readable medium. In various different implementations, thestorage device 630 may be a floppy disk device, a hard disk device, anoptical disk device, or a tape device.

The input/output device 640 provides input/output operations for thesystem 600. In one implementation, the input/output device 640 includesa keyboard and/or pointing device. In another implementation, theinput/output device 640 includes a display unit for displaying graphicaluser interfaces.

The features described can be implemented in digital electroniccircuitry, or in computer hardware, firmware, software, or incombinations of them. The apparatus can be implemented in a computerprogram product tangibly embodied in an information carrier, e.g., in amachine-readable storage device or in a propagated signal, for executionby a programmable processor; and method steps can be performed by aprogrammable processor executing a program of instructions to performfunctions of the described implementations by operating on input dataand generating output. The described features can be implementedadvantageously in one or more computer programs that are executable on aprogrammable system including at least one programmable processorcoupled to receive data and instructions from, and to transmit data andinstructions to, a data storage system, at least one input device, andat least one output device. A computer program is a set of instructionsthat can be used, directly or indirectly, in a computer to perform acertain activity or bring about a certain result. A computer program canbe written in any form of programming language, including compiled orinterpreted languages, and it can be deployed in any form, including asa stand-alone program or as a module, component, subroutine, or otherunit suitable for use in a computing environment.

Suitable processors for the execution of a program of instructionsinclude, by way of example, both general and special purposemicroprocessors, and the sole processor or one of multiple processors ofany kind of computer. Generally, a processor will receive instructionsand data from a read-only memory or a random access memory or both. Theessential elements of a computer are a processor for executinginstructions and one or more memories for storing instructions and data.Generally, a computer will also include, or be operatively coupled tocommunicate with, one or more mass storage devices for storing datafiles; such devices include magnetic disks, such as internal hard disksand removable disks; magneto-optical disks; and optical disks. Storagedevices suitable for tangibly embodying computer program instructionsand data include all forms of non-volatile memory, including by way ofexample semiconductor memory devices, such as EPROM, EEPROM, and flashmemory devices; magnetic disks such as internal hard disks and removabledisks; magneto-optical disks; and CD-ROM and DVD-ROM disks. Theprocessor and the memory can be supplemented by, or incorporated in,ASICs (application-specific integrated circuits).

To provide for interaction with a user, the features can be implementedon a computer having a display device such as a CRT (cathode ray tube)or LCD (liquid crystal display) monitor for displaying information tothe user and a keyboard and a pointing device such as a mouse or atrackball by which the user can provide input to the computer.

The features can be implemented in a computer system that includes aback-end component, such as a data server, or that includes a middlewarecomponent, such as an application server or an Internet server, or thatincludes a front-end component, such as a client computer having agraphical user interface or an Internet browser, or any combination ofthem. The components of the system can be connected by any form ormedium of digital data communication such as a communication network.Examples of communication networks include, e.g., a LAN, a WAN, and thecomputers and networks forming the Internet.

The computer system can include clients and servers. A client and serverare generally remote from each other and typically interact through anetwork, such as the described one. The relationship of client andserver arises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other.

A number of embodiments have been described. Nevertheless, it will beunderstood that various modifications may be made without departing fromthe spirit and scope of this disclosure. Accordingly, other embodimentsare within the scope of the following claims.

What is claimed is:
 1. A computer-implemented method for performing selective viewing of a scene, the method comprising: acquiring an image of a real scene using a camera; identifying, in the acquired image, a first object in the real scene located on a first side of a virtual plane defined for the real scene and a second object located on a second side of the virtual plane; modifying the acquired image by removing image content corresponding to the identified first object, wherein image content corresponding to the identified second object is not removed based on the second object being located on the second side; and displaying the modified acquired image to a person performing surveillance of the real scene, wherein the virtual plane is defined at a specific location in a passageway in the real scene such that any object passing through the virtual plane in the passageway is only visible in the modified acquired image while on one of the first and second sides.
 2. The computer-implemented method of claim 1, wherein the image is acquired as part of continuously acquiring a live image of the real scene, and wherein during a duration of the acquired live image the first object moves between a location behind the virtual plane and a location in front of the virtual plane, as seen from the camera.
 3. The computer-implemented method of claim 2, further comprising: modifying the acquired live image so that the first object is visible in the modified acquired live image only when the first object is in front of the virtual plane.
 4. The computer-implemented method of claim 2, further comprising: modifying the acquired live image so that the first object is visible in the modified acquired live image only when the first object is behind the virtual plane.
 5. The computer-implemented method of claim 1, wherein a shape defines the virtual plane, the method further comprising: replacing any image contents within the shape with substitute content that does not include the first object.
 6. The computer-implemented method of claim 5, further comprising: acquiring the substitute content by acquiring another image of the real scene while the first object is not present on the first side of the virtual plane.
 7. The computer-implemented method of claim 1, wherein a shape defines the virtual plane, the method further comprising: determining that the first object is on the first side by identifying that image content corresponding to at least part of the first object has a predefined location relative to a border of the shape.
 8. The computer-implemented method of claim 7, wherein the image is acquired as part of continuously acquiring a live image of the real scene, the method further comprising: modifying the acquired live image by erasing any image content within the shape and placing substitute content within the shape that does not include the first object; identifying that the first object moves in the real scene, wherein the first object is not visible in the modified acquired live image while the first object is on the first side; determining, based on the identification, that the first object moves past the shape to the second side; and ceasing to remove content corresponding to the first object from the modified acquired live image based on the determination.
 9. The computer-implemented method of claim 1, further comprising: determining that the first object is on the first side by analyzing a size of the first object in the acquired image using a map of the real scene.
 10. The computer-implemented method of claim 1, further comprising: determining that the first object is on the first side by determining a distance from the first object to the camera.
 11. The computer-implemented method of claim 10, wherein the first object is a human being and wherein the distance is determined using a size of a part of the human being measured in the acquired image.
 12. The computer-implemented method of claim 1, wherein the virtual plane is defined by a virtual polygon.
 13. The computer-implemented method of claim 1, wherein the modified acquired image is displayed to the person substantially in real time.
 14. The computer-implemented method of claim 1, wherein the modified acquired image is displayed for low-security level observation, further comprising recording the acquired image for high-security level observation.
 15. The computer-implemented method of claim 1, wherein a shape defines the virtual plane, the shape comprising at least one hole.
 16. A computer-implemented method for performing selective viewing of a scene, the method comprising: acquiring an image of a real scene using a camera; identifying, in the acquired image, a first object in the real scene located on a first side of a virtual plane defined for the real scene and a second object located on a second side of the virtual plane; modifying the acquired image by removing image content corresponding to the identified first object, wherein image content corresponding to the identified second object is not removed based on the second object being located on the second side; and displaying the modified acquired image to a person performing surveillance of the real scene, wherein the image is acquired as part of continuously acquiring a live image of the real scene, and wherein during a duration of the acquired live image the first object moves between a location behind the virtual plane and a location in front of the virtual plane, as seen from the camera.
 17. The computer-implemented method of claim 16, further comprising: modifying the acquired live image so that the first object is visible in the modified acquired live image only when the first object is in front of the virtual plane.
 18. The computer-implemented method of claim 16, further comprising: modifying the acquired live image so that the first object is visible in the modified acquired live image only when the first object is behind the virtual plane.
 19. A computer-implemented method for performing selective viewing of a scene, the method comprising: acquiring an image of a real scene using a camera; identifying, in the acquired image, a first object in the real scene located on a first side of a virtual plane defined for the real scene and a second object located on a second side of the virtual plane; modifying the acquired image by removing image content corresponding to the identified first object, wherein image content corresponding to the identified second object is not removed based on the second object being located on the second side; displaying the modified acquired image to a person performing surveillance of the real scene; and determining that the first object is on the first side by analyzing a size of the first object in the acquired image using a map of the real scene.
 20. A computer-implemented method for performing selective viewing of a scene, the method comprising: acquiring an image of a real scene using a camera; identifying, in the acquired image, a first object in the real scene located on a first side of a virtual plane defined for the real scene and a second object located on a second side of the virtual plane; modifying the acquired image by removing image content corresponding to the identified first object, wherein image content corresponding to the identified second object is not removed based on the second object being located on the second side; displaying the modified acquired image to a person performing surveillance of the real scene; and determining that the first object is on the first side by determining a distance from the first object to the camera. 